As pointed out in my co-pending U.S. patent application Ser. No. 12/152,319, filed May 13, 2008, there are many types of poles for a wide range of applications, such as streetlights, fence posts, flagpoles, utility poles and sign poles. The term poles as used herein encompasses both relatively short poles, commonly called posts, as well as poles of greater length.
The current methods of pole installation can be grouped into 3 categories. (1) The simplest category involves driving a pole into the ground with a post driver; it is commonly used for installing short sign poles and fence poles. (2) The second category requires digging a hole into the ground first, the pole then being placed into the hole, and native soil compacted around the pole. Instead of using compacted soil, expandable foam, cement or concrete are also commonly used to secure the pole inside the hole. This method is used in many applications such as fence posts, flagpoles, utility poles and tall sign poles. The installation cost is higher than the first approach, but it is currently the cheapest way to install tall poles. (3) The third approach is to build a reinforced concrete foundation with anchor bolts or other fasteners protruding from the top of the concrete foundation for pole attachment. A hole in the ground is still needed to embed the concrete foundation. With this approach, the pole is set on top of the foundation. Tall poles or poles requiring strong base connection typically use this third approach; examples include tall street lamps, utility poles and flagpoles. This is the costliest of the three methods, but is also the strongest for heavy loading. When electrical wires are required, such as for street lamps, conduit is embedded into the concrete foundation or introduced underground from a side of the pole. Once wires are pulled inside the base of the pole, wire connection is done through a “hand hole” at the bottom of the pole. These prior art approaches have been practiced for many years and are effective in many ways. However, they do have limitations and shortcomings as listed below:
The installation practice of Category 1 is simple, efficient and low cost. A major drawback is the limited length of the pole it can handle. It is difficult and not safe to drive a tall pole into the ground, and some poles such as flagpoles are not designed for driving.
The installation approach of Category 2 can handle tall poles of various types. The installation cost is higher than Category 1. Except for very small poles, it requires at least two people and often includes auger and lifting equipment to dig a deep hole and put the pole in place. Further, removing the pole will involve significant efforts and costs.
The approach of Category 3, in addition to the cost and time of a reinforced foundation, involves a second trip to install the pole after the concrete is set. In most cases, it requires at least a two-man crew, auger and lifting equipment. Pole removal is also very costly.
To simplify installation, and make pole servicing easier, it is known to employ a hinged base to allow easier raising and lowering of a pole. This is a variation of the Category 3 approach. U.S. Pat. Nos. 4,079,559 and 6,216,414 disclose two examples. In these examples, the pole connections to the base are very strong. U.S. Pat. No. 5,058,336 uses a cumbersome hydraulic ram to raise and lower a pole, and its base hinge connection is weak. Weaker materials such as wood will not work well for the pole base. Moreover, these prior art installations suffer the same problems as mentioned above in connection with Category 3.
The prior art installations in general are limited in efficiency and versatility. Many steps and resources are involved during installation. Since at least two people are often required, it is highly inefficient when installing small numbers of poles; driving time alone can be costly. A system allowing only one person installation can yield huge savings for small quantity jobs. Further, as removing poles installed using the prior art approaches is difficult, they are not efficient for temporary applications such as temporary power poles and temporary surveillance camera poles. Electrical wiring installation using the prior art systems is also rather clumsy. Maintenance, such as changing light bulbs, equipment or components thereof can also be challenging, since elevated equipment such as a bucket truck is often necessary. The hinged base poles are better for servicing, but their pole base installations are far from desirable.
The following prior art is believed to be further representative of the current state of the prior at in this field: U.S. Pat. No. 6,955,025, U.S. Pat. No. 7,275,351, U.S. Pat. No. 5,782,040, U.S. Pat. No. 3,680,448, U.S. Pat. No. 6,390,436, U.S. Pat. No. 6,264,162, U.S. Pat. No. 3,267,627, U.S. Pat. No. 3,820,906, U.S. Pat. No. 6,428,242, U.S. Pat. No. 3,792,980, U.S. Pat. No. 4,926,592, U.S. Pat. No. 6,851,231, U.S. Pat. No. 6,399,881, U.S. Pat. No. 6,191,355, U.S. Pat. No. 3,895,471, U.S. Pat. No. 7,267,516, U.S. Pat. No. 6,709,215, U.S. Pat. No. 5,899,651, U.S. Pat. No. 5,634,759, U.S. Pat. No. 5,794,378, U.S. Pat. No. 6,322,038, U.S. Pat. No. 3,112,037, U.S. Pat. No. 639,286, U.S. Pat. No. 5,476,352, U.S. Pat. No. 4,362,451, U.S. Pat. No. 4,492,496, U.S. Pat. No. 3,190,465, U.S. Pat. No. 4,114,766 and U.S. Pat. No. 2,792,948.
The pole installation system of my above-identified co-pending U.S. patent application addressed a number of shortcomings of other pole systems and is particularly useful for installing heavy poles quickly by one person. However, it requires the installation of an anchor pole in the ground, and equipment for large hole drilling or post driving is needed. For tall poles, the embedment depth of the anchor poles usually has to be very deep.